1. Field of the Invention
This invention relates to a stereo eye fundus camera including an illuminating optical system for illuminating the fundus of an eye to be tested through an objective lens and a taking optical system for taking the eye fundus through the objective lens.
2. Prior Art of the Invention
Heretofore, a stereo eye fundus camera of the type shown in FIGS. 8 and 9 has been known. This conventional stereo eye fundus camera includes an objective lens 2 faced with an eye 1 to be tested, a taking system 3 for taking the fundus 1b of the eye 1, and an illuminating optical system 4 for illuminating the eye fundus 1b. The taking system 3 includes a beam splitting optical system for splitting beam passing through the objective lens 2 in order to see the object stereoscopically, a taking optical system 7 for taking the eye fundus, and an observing optical system k.
The beam splitting optical system 5 comprises a beam splitter 8 for splitting beam, a circular aperture diaphragm 9 having circular apertures (not shown) in symmetrical positions, and relay lenses 10a, 10b.
The taking optical system 7 comprises an image erecting poloprism 16a, 16b, etc. The numeral 17 denotes a taking lens. An observing optical system K comprises reflecting mirrors 11a, 11b, 12a, and 12b, an image erecting prisms 13a and 13b, field lenses 14a and 14b, eyepiece 15a and 15b, etc.
The illuminating optical system 4 comprises a perforated mirror V having an elongated opening (not shown), a condenser lens 18, a reflecting mirror 19, a relay lens 20, a shading plate 21 having a shading portion (not shown) formed on a central portion of its circular transparent plate, a half mirror 22, a condenser lens 23, an illuminating light source 24, a condenser lens 25, a taking light source 26, etc.
The beam emitted by an illuminating light source 24 passes through the condenser lens 23, the half mirror 22, the shading plate 21, the relay lens 20, the reflecting mirror 19, the condenser lens 18, the perforated mirror V and the objective lens 2 and illuminates the fundus 1b of the eye 1 to be tested. The shading plate 21 is conjugated with the pupil 1a of the eye 1 so that the image of the plate 21 is formed on the pupil 1a and the illuminating light is not made incident to the vicinity of the central portion of the pupil 1a.
The light reflected by the eye fundus 1b passes through the objective lens 2 and the elongated opening of the perforated mirror V and is then split into two portions by the beam splitting optical system 5. The split beam passes through the relay lenses 10a and 10b, the reflecting mirrors 11a, 11b, 12a and 12b, the image erecting prisms 13a and 13b, the field lenses 14a and 14b, and the eyepiece 15a and 15b and reaches observing eyes Q1 and Q2 by which the eye fundus 1b is stereoscopically observed.
When taking a photograph, the reflecting mirrors 11a and 11b are removed from the optical path and the taking light source 26 is lighted up. A pair of eye fundus images obtained when the eye fundus is viewed from both sides are taken in the taking film 17.
When the eye fundus is stereoscopically analyzed from the pair of eye fundus images, firstly, the common points to the pair of images are at least at three points plotted on two image screens so that the common points are not situated on the same straight line, and a mutual fixed position is occupied based thereon. Then, errors are found for each and every corresponding points on the image screens and the stereoscopic configurations of a papilla portion, etc. are analyzed.
However, in the above-mentioned stereo eye fundus camera, plotting of the fixed points must be manually performed by the operator and therefore the working is troublesome. There is also such a problem as that the correctly corresponding positions of the fixed points which are often at the crossing positions of the common blood vessels, brim of papilla, etc. to the two image screens are very difficult to find.